CORE - Namespace for Perl's core routines
BEGIN { *CORE::GLOBAL::hex = sub { 1; }; } print hex("0x50"),"\n"; # prints 1 print CORE::hex("0x50"),"\n"; # prints 80 CORE::say "yes"; # prints yes BEGIN { *shove = \&CORE::push; } shove @array, 1,2,3; # pushes on to @array
The CORE namespace gives access to the original built-in functions of Perl. The CORE package is built into Perl, and therefore you do not need to use or require a hypothetical "CORE" module prior to accessing routines in this namespace.
CORE
A list of the built-in functions in Perl can be found in perlfunc.
For all Perl keywords, a CORE:: prefix will force the built-in function to be used, even if it has been overridden or would normally require the feature pragma. Despite appearances, this has nothing to do with the CORE package, but is part of Perl's syntax.
CORE::
For many Perl functions, the CORE package contains real subroutines. This feature is new in Perl 5.16. You can take references to these and make aliases. However, some can only be called as barewords; i.e., you cannot use ampersand syntax (&foo) or call them through references. See the shove example above. These subroutines exist for all keywords except the following:
&foo
shove
__DATA__, __END__, and, cmp, default, do, dump, else, elsif, eq, eval, for, foreach, format, ge, given, goto, grep, gt, if, last, le, local, lt, m, map, my, ne, next, no, or, our, package, print, printf, q, qq, qr, qw, qx, redo, require, return, s, say, sort, state, sub, tr, unless, until, use, when, while, x, xor, y
__DATA__
__END__
and
cmp
default
do
dump
else
elsif
eq
eval
for
foreach
format
ge
given
goto
grep
gt
if
last
le
local
lt
m
map
my
ne
next
no
or
our
package
print
printf
q
qq
qr
qw
qx
redo
require
return
s
say
sort
state
sub
tr
unless
until
use
when
while
x
xor
y
Calling with ampersand syntax and through references does not work for the following functions, as they have special syntax that cannot always be translated into a simple list (e.g., eof vs eof()):
eof
eof()
chdir, chomp, chop, defined, delete, each, eof, exec, exists, keys, lstat, pop, push, shift, splice, split, stat, system, truncate, unlink, unshift, values
chdir
chomp
chop
defined
delete
each
exec
exists
keys
lstat
pop
push
shift
splice
split
stat
system
truncate
unlink
unshift
values
To override a Perl built-in routine with your own version, you need to import it at compile-time. This can be conveniently achieved with the subs pragma. This will affect only the package in which you've imported the said subroutine:
subs
use subs 'chdir'; sub chdir { ... } chdir $somewhere;
To override a built-in globally (that is, in all namespaces), you need to import your function into the CORE::GLOBAL pseudo-namespace at compile time:
CORE::GLOBAL
BEGIN { *CORE::GLOBAL::hex = sub { # ... your code here }; }
The new routine will be called whenever a built-in function is called without a qualifying package:
print hex("0x50"),"\n"; # prints 1
In both cases, if you want access to the original, unaltered routine, use the CORE:: prefix:
print CORE::hex("0x50"),"\n"; # prints 80
This documentation provided by Tels <nospam-abuse@bloodgate.com> 2007.
perlsub, perlfunc.
To install vars, copy and paste the appropriate command in to your terminal.
cpanm
cpanm vars
CPAN shell
perl -MCPAN -e shell install vars
For more information on module installation, please visit the detailed CPAN module installation guide.